I believe that Sora's KK is just a version of the term "Keyblade". Because, when you got other kinds of keyblades, to equip them it says "Keychains", not "Keyblades".
The KK, judging by the IKK, is the basic, standard form of that Keyblade. The fact he received it as such from Riku kind of supports that notion.
It's one form out of many, yes, but it's the one that 'should be', hence why it's also the official one for him.
I think the Keychains were just ways to access other keyblades.
Regardless of the Keychain, Sora's using the same base Keyblade all through the series.
All the keyblades Sora uses have keychains.
Because the base had a Keychain, hence why it could be costumized with other Keychains. It's still one and the same Keyblade.
WtD did too, and so did the fagkey. And they're all different.
Riku's Keychain is based on other things than what Sora's Keychains are, so of course they'd be different.
There's still only two Keyblades in play here, being Sora's (which he can Duel Wield), and Riku's (which he could also Duel Wield, at least as Rikunort)
Possibly the keyblade is one concept and the Keychains are awarded to those with strong enough hearts as upgrades.
The term "upgrade" relates to gameplay mechanics. They have a deeper meaning, hence why they bothered to have Keyblades that
lack Keychains. This probably relates to TAV's status as Apprentices as opposed to Riku and Sora who have been ranked from Masters to proper Wielders.
It was created from the darkness in his heart, but it took shape with Malificent's magic.
You're basing this on KHWiki, right? However, if you ask Nomura...
Another Report said:
However there is no particular explanation for the Soul Eater’s transfer and occurence
You'll see it was never really explained properly.
Unless someone wants to enlighten us all from a novel paragraph or something.
Yet they weren't trained thus the they don't have to be in order to wield they just have to be chosen...
Their Hearts are "Master level". That's good enough.
Why is the "Lost Two" believed to be 2 of TAV?
My own personal beliefs and preferences.
Something I've been wondering and can't even remember asking before yet have the slightest feeling I have...What gives Terra the authority to "choose" a wielder? Just cause his emblem is gold?
It would appear that for now, the answer is "he
could, hence he
did."